<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .main{
            width: 600px;
            display: flex;
        }
        .div1{
            width: 50%;
            height: 500px;
            background-color: rgb(12, 151, 82);
        }
        .div2{
            width: 50%;
            flex: 1;
            background-color: aqua;
        }
    </style>
</head>

<body>
    <div class="main">
        <div class="div1"></div>
        <div class="div2"></div>
    </div>
</body>

</html>